Manufacturing technology to produce phenol and acetone via the oxidation of cumene to cumene hydroperoxide and the subsequent decomposition of peroxide to phenol and acetone is well known and widely employed commercially. Numerous by-products, such as phenyl alcohols, aldehydes, and ketones, are also produced in the oxidation/decomposition process. One such by-product, acetophenone, is especially useful as an intermediate for the production of pharmaceuticals and specialty perfumes. Acetophenone also exhibits unique solvent properties useful in the manufacturing and processing of gums and resins.
Acetophenone from a phenol process is available only in the form of low purity product, generally less than 20%, and is contained in the plant waste heavies stream, which is typically burned for fuel value. Separation of the acetophenone and subsequent purification is extremely difficult due to the close proximity of its boiling point to azeotropes of other materials contained in the waste heavies, namely phenol and 2-phenyl propionaldehyde (2-PPA). Conventional distillation cannot be used to yield high purity acetophenone. The recovery of such products has been attempted in the past, but most such recovery processes are complex operations. Thus, in a process of separating acetophenone and 2-phenyl propionaldehyde (also called hydratropic aldehyde), the mixture is treated with an aqueous sodium bisulfite solution which with the latter forms a water soluble adduct. Acetophenone does not and, being insoluble in the aqueous solution, can be separated from it. This process is described in U.S. Pat. No. 3,379,768.
The present invention is directed toward a novel and improved method of separating acetophenone from a mixture thereof which contains phenol, 2-PPA, and phenolic heavies. Phenol can be separated from the other components by extraction with sodium hydroxide. The phenol in the form of sodium phenate, is soluble in the aqueous phase and can be later recovered as phenol using acid treatment. The remaining 2-PPA and acetophenone, having been separated from the aqueous phase, are catalytically reacted at high temperatures in the presence of caustic to form 1,4-diphenyl-3-hydroxy-1-pentanone and subsequently dehydrated to form 1,4-diphenyl-2-penten-1-one, 1,4-diphenyl-3-penten-1-one, and isomers thereof. The remaining acetophenone, being present in significantly larger amounts, can now be easily purified and separated from the heavy pentanones and pentenones by vacuum distillation.